15N Solid State NMR Spectroscopic Study of Surface Amine Groups for Carbon Capture: 3-Aminopropylsilyl Grafted to SBA-15 Mesoporous Silica,Environmental Science & Technology

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15N Solid State NMR Spectroscopic Study of Surface Amine Groups for Carbon Capture: 3-Aminopropylsilyl Grafted to SBA-15 Mesoporous Silica
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2018-01-10 00:00:00 , DOI: 10.1021/acs.est.7b04555
Daphna Shimon ₁ , Chia-Hsin Chen ₁ , Jason J. Lee ₂ , Stephanie A. Didas ₂ , Carsten Sievers ₂ , Christopher W. Jones ₂ , Sophia E. Hayes ₁

Affiliation

Materials composed of high-porosity solid supports, such as SBA-15, containing amine-bearing moieties inside the pores, such as 3-aminopropylsilane (APS), are envisioned for carbon dioxide capture; solid-state ¹⁵N NMR can be highly informative for studying chemisorption reactions. Two ¹⁵N-enriched samples with different APS loadings were studied to probe the identity of the pendant molecules and structure of the chemisorbed CO₂ species. ¹⁵N cross-polarization magic-angle spinning NMR provides unique information about the amines, whether they are rigid or dynamic, by measuring contact time curves and rotating frame, T_1ρ(¹⁵N), relaxation. Both carbamate and carbamic acid are formed; carbamic acid is shown to be less stable than carbamate. After desorption, a steady state for the chemisorbed reaction product is reached, leaving behind carbamate. ¹⁵N NMR monitors the evolution of the species over time. During desorption, APS is regenerated, but the ammonium propylsilane intensity does not change, leading us to conclude that carbamic acid desorbs, while carbamate (to which ammonium propylsilane is ion paired) persists. A secondary ditehtered amine present does not react with CO₂, and we posit this may be due to its rigidity. These findings demonstrate the versatility of solid-state NMR to provide information about these complex CO₂ reactions with solid amine sorbents.

中文翻译：

用于碳捕获的表面胺基团的¹⁵ N固态NMR光谱研究：接枝到SBA-15中孔二氧化硅的3-氨基丙基甲硅烷基

设想由高孔隙率固体载体（例如SBA-15）组成的材料在孔内含有含胺部分（例如3-氨丙基硅烷（APS））用于二氧化碳捕集；固态¹⁵ N NMR对于研究化学吸附反应可能非常有用。研究了两个¹⁵种富含APS的N富集样品，以研究侧链分子的身份和化学吸附的CO ₂物种的结构。¹⁵ N交叉极化魔角旋转NMR通过测量接触时间曲线和旋转框架_T1ρ（¹⁵N），放松。氨基甲酸酯和氨基甲酸都形成；已显示氨基甲酸的稳定性不如氨基甲酸酯。解吸后，化学吸附的反应产物达到稳定状态，剩下氨基甲酸酯。¹⁵ N NMR监测物种随时间的演变。在解吸过程中，APS会再生，但丙基丙基硅烷铵的强度不会改变，这使我们得出结论，氨基甲酸会解吸，而氨基甲酸酯（与丙基丙基铵铵成对的氨基甲酸酯）会持续存在。存在的仲二胺不与CO ₂反应，我们认为这可能是由于其刚性。这些发现证明了固态NMR的多功能性，可提供有关这些与固体胺吸附剂进行的复杂CO ₂反应的信息。

更新日期：2018-01-10

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